Mercedes C63 misfire

[stuart v]

Hi everybody,just wondered if anyone has had a similar problem.Car runs fine under full power and very light throttle opening but on autobahns under medium throttle opening engine misfires and tachometer flutters slightly.This happens from 2000 rpm up to 3500.If you floor it it pulls cleanly.Have changed plugs and air filters for k+n.Any advice welcome.Have had it remapped by msl but problem was there before,cheers,Stuart.2008 C63.

[lee c63]

Check the gaps on the spark plugs. Had something similar on mine which only happened when it was ticking over. Are you getting any warning lights?

[stuart v]

Hi Lee,checked gaps on new plugs before fitting,no change after fitting.Idle is ok,just misfiring at part throttle.Feels like one or two cylinders are not firing cleanly.Will remove plugs and check colour and gaps again,many thanks,Stuart.

[stuart v]

Forgot to add no warning lights showing,do you know the best hand held fault code reader?Hope yours is going strong.

[lee c63]

stuart v said:

Forgot to add no warning lights showing,do you know the best hand held fault code reader?Hope yours is going strong.

Can't really help for the code reader...I have a cheap one from e bay and then just google the codes.
Has it started just since the re-map and plug change?

Mine is still running good thanks.

[stuart v]

Hi Lee,no,but i did not notice it before fitting the k+n filters.Dont know if the oil from the filters has contaminated the mafs.Thanks for the advice,cheers,Stuart

[ecain63]

stuart v said:

Hi Lee,no,but i did not notice it before fitting the k+n filters.Dont know if the oil from the filters has contaminated the mafs.Thanks for the advice,cheers,Stuart

That'd be my bet. Not all cars like oiled filters.